Investigating the Sedimentary Structure of the Baza Basin (Southern Spain) using Seismic Reflection Profiling

The Baza Basin is an intra-mountain evaporitic basin in Southern Spain. It is the largest of the Late Neogene continental basins of the Betic Cordillera. During the last 7 million years the basin alternately was flooded and fell dry. Therefore, up to 2.5 km thick lacustrine and ancillary continental deposits are found which provide an unique archive of climatic changes and paleo-climatic events. Plans exist to analyze the sedimentary record with regard to the paleo-climate in the Mediterranean as well as on a global scale within a scientific drilling project. In preparation for the future drilling activities, controlled-source seismic measurements are used to investigate the structure of the Baza Basin and to find local zones of neo-tectonic deformation bounding the basin to the west (Baza fault). In October 2013 a seismic reflection experiment was carried out in the center of the Baza Basin. A net of three 2D seismic profiles was arranged crossing the basin and the bounding fault system. A vibroseis source (two vibrators with 200 kN peak force each) was used with a source point distance of 60 m along each of the 18 km long profiles. Eight sweeps with a frequency range of 8 ­- 100 Hz were conducted at each source point. The seismic wavefield was recorded by a cable-free acquisition system of more than 330 continuously operating digital data recorders. The receivers were spread along the currently active profile with a spacing of 20 m. They were moved in a roll-along-configuration to mainly cover the near-field offsets of the source points. The seismic data of the three profiles were conventionally processed so far. Tomographic inversion of the first arrivals (P-waves) provide additional information. The images show the asymmetrical basin geometry. Several seismic sequences and the basement can be identified. Furthermore, the Baza fault system and a series of other - previously unknown - faults can be seePeer Reviewe

2D characterization of near-surface V P/V S: surface-wave dispersion inversion versus refraction tomography

International audienceThe joint study of pressure (P-) and shear (S-) wave velocities (Vp and Vs ), as well as their ratio (Vp /Vs), has been used for many years at large scales but remains marginal in near-surface applications. For these applications, and are generally retrieved with seismic refraction tomography combining P and SH (shear-horizontal) waves, thus requiring two separate acquisitions. Surface-wave prospecting methods are proposed here as an alternative to SH-wave tomography in order to retrieve pseudo-2D Vs sections from typical P-wave shot gathers and assess the applicability of combined P-wave refraction tomography and surface-wave dispersion analysis to estimate Vp/Vs ratio. We carried out a simultaneous P- and surface-wave survey on a well-characterized granite-micaschists contact at Ploemeur hydrological observatory (France), supplemented with an SH-wave acquisition along the same line in order to compare Vs results obtained from SH-wave refraction tomography and surface-wave profiling. Travel-time tomography was performed with P- and SH- wave first arrivals observed along the line to retrieve Vtomo p and Vtomo s models. Windowing and stacking techniques were then used to extract evenly spaced dispersion data from P-wave shot gathers along the line. Successive 1D Monte Carlo inversions of these dispersion data were performed using fixed Vp values extracted from Vtomo p the model and no lateral constraints between two adjacent 1D inversions. The resulting 1D Vsw s models were then assembled to create a pseudo-2D Vsw s section, which appears to be correctly matching the general features observed on the section. If the pseudo-section is characterized by strong velocity incertainties in the deepest layers, it provides a more detailed description of the lateral variations in the shallow layers. Theoretical dispersion curves were also computed along the line with both and models. While the dispersion curves computed from models provide results consistent with the coherent maxima observed on dispersion images, dispersion curves computed from models are generally not fitting the observed propagation modes at low frequency. Surface-wave analysis could therefore improve models both in terms of reliability and ability to describe lateral variations. Finally, we were able to compute / sections from both and models. The two sections present similar features, but the section obtained from shows a higher lateral resolution and is consistent with the features observed on electrical resistivity tomography, thus validating our approach for retrieving Vp/Vs ratio from combined P-wave tomography and surface-wave profiling

Cultuurberichtgeving in een tijdperk van globalisering

This article aims at charting and elucidating key developments and cross-national variations in the coverage given to foreign and indigenous cultural products (classical and popular music, dance, film, literature, theater, television fiction, and visual arts) in American, Dutch, French, and German newspapers between 1955 and 2005. Using content analysis, it is first explored to what extent the explosive growth of international cultural traffic in the second half of the twentieth century has been accompanied by increased newspaper coverage of foreign arts and culture in the four countries under study. Second, the article examines the assumption that the degree and direction of international orientation differs among countries according to their size, the centrality of their cultural production or their production in particular cultural fields, and their cultural policy framework. Third, the article qualifies the evolving patterns of dominance in the international orientation of arts journalism in each country, in terms of countries and regions represented in arts and culture coverage